What is the ruling on one who abandoned prayer due to obsessive whispers (waswās), uttered phrases indicating despair and discontent with God's decree, felt comfortable reading material that calls for turning away from religion, yet without denying religion, and what should he do regarding his acts of worship during that period?

These words are among the reprehensible utterances that can expel one from the fold of faith. If they were uttered under the influence of illness, then there is no sin upon you. However, if they were uttered by your own choice, then you must perform sincere repentance, for "the one who repents from sin is like one who has no sin." If you have repented before, then your acts of worship after repentance are valid and accepted.